Nature Chem. http://doi.org/m5w (2013)

Organic fluorophores are commonly used as probes in fluorescence studies of biological systems. Their application, however, is often hampered by their photostability. To overcome this, anti-fading agents or oxygen-scavenging enzymes can be added but these may introduce toxicity issues. Now, Steven Zimmerman and colleagues have designed a single-molecule, far-red fluorescent probe that shows longer-lasting fluorescence emission and more stable, and reduced blinking emission than the cyanine fluorophore, Cy5. This enhanced emission behaviour is observed in the absence of anti-fading additives but in the presence of oxygen-scavenging agents. The probe comprises a water-soluble polyglycerol dendritic structure covalently coupled to a ring-fused boron-containing fluorophore and a targeting moiety such as biotin. The non-blinking behaviour of the dendritic fluorophore is attributed to the ring-fused arrangement of the boron-containing moiety and, to a lesser extent, the shielding nature of the dendritic arm. Preliminary in vitro experiments demonstrate the imaging of the microtubule network of mouse embryonic fibroblast cells as a result of neutrAvidin–biotin interactions.